Pyrolysis of nitrogen bases



April 8, 1941. BAlLEY ETAL 2 ,237,541

PYROLYSIS OF NITROGEN BASES Filed June 26, 1937 INVEN'IORS JRBazZey &Raymond Mahan ATTORNEY- Patented Apr. 8, 1941 PYROLYSIS OF NITROGENBASES James K. Bailey and Raymond Mahan, Austin, Tex, assignors to UnionOil Company of California, Los Angeles, Calif., a. corporation ofCalifornia ApplicationJune 26, 1937, Serial No. 150,637 2 Claims. (Cl.260--290) This invention relates to pyrolysis of nitrogen bases and to amethod for the production of pyridine, quinoline and pyrrole and theiralkylated homologs. More specifically the invention relates to a methodfor the production of pyridine and quinoline homologs from complex basicnitrogen compounds.

We have discovered that certain nitrogen containing compounds found inpetroleum, coal tar, shale oil, oil obtained by pyrolysis of suchprotein material ascotton seed meal and more specifically, Californiaasphalt-base petroleum, can be converted into other nitrogenouscompounds by our process of pyrolysis.

According to our invention, nitrogen containing compounds such aspyridines, isopyridines, and polynuclear bases containing condensed ringsystems or mixtures of crude nitrogen bases of analogous structure, suchas the crude bases obtained from petroleum distillates, are subjected totreatment with heat or with heat in the presence of a suitable catalystand at suitable pressure, to form interalia simpler pyridines orquinolines. The reactions induced by our process may comprisedehydrogenation, ring cleavvided with a two hole stopper l1.

5,. stopper I1 is also provided with a tube t one tube employed in thefigure is 24 inches long and age, dealkylation, and the like, orcombinations of these reactions, but in general the effect is toincrease the aromaticity of the bases so treated. Aromatic bases, whichcomprise pyridines and quinolines, are characterized, incontradistinction to non-aromatic or hydro-aromatic bases, by a highrefractive index for a given molecular weight, by a relatively highcarbon to hydrogen ratio, and by the preferential solution of theirhydrochlorides in water in the presence of ch10- roform. According tothe character of base or bases taken for treatment and the conditions orpyrolysis our process may result in either lower boiling simplemolecules or in higher boiling molecules, but in any case our processconverts Through one of the holes in stopper ll there is inserted a tubeI which extends downward into the flask 2 and terminates beneath thesurface of the crude nitrogen base material 3. The other hole of end ofwhich terminates in the vapor space of flask 2. The other end of tube 4is connected with Jena glass tube 6 which is positioned within theheating space of furnace 5. The Jena glass inch inside diameter withapproximately 12 inches of this tube exposed to direct heat of thefurnace 5. The other end of tube 6 is connected to tube 1 which passesthrough the single hole cork or stopper 8 into separating flask 9. Tube1 terminates within about 1% inches from the bottom of flask 9. Flack 9is provided with a side tube It directly underneath stopper 8. The sidetube l8 connected to tube l0 passes through the one hole stopper Hfitted to flask l2. Tube l0 terminates about 1 inches from the bottom offlask I2. In order to maintain flask l2 cool it is immersed in beaker orjar l3 which is filled with ice. The side tube M of flask i2 isconnected with U-tube l5 which is filled with glass wool I6 moistenedwith concentrated sulphuric acid.

In carrying out, the pyrolysis of nitrogen base material according toour invention, flask 2 was charged with a measured quantity of nitrogenbase material having the formula C16H25N and believed to be methylateddihydroisopyrindine, This material was derived from kerosene bases inthe 275-280 C. boiling range as follows:

The crude bases were dissolved in an equal volume of GNHCl and thehydrochlorides extracted with a volume of chloroform equal to the volumeof the bases. The non-aromatic or hydroaromatic base hydrochloridespassed into the chloroiorm. layer and on distilling the chloroform It isa further obour invention. Referring to the figure, container 2 is aflask for holding the crude nitrogen base material for treatment. Thisflask isproble in water and very soluble in organic solvents.

A more complete description of this base may be found together with themethod of isolation in the Journal of the American Chemical Society,volume 53, page 1007. i

Natural gas was admitted into tube l and forced into flask 2 beneath thesurface of the nitrogen base stock 3. The content 3, of flask 2 washeated by means of burner I9 in order to facilitate passage of the basevapors into tube 6. The natural gas, laden with the vapors of the crudenitrogen base material was thus passed through tube 4 into tube 6positioned within the heating zone of furnace 5. Here the temperature ofthe nitrogen base material was raised to approximately 700 C, The heatedmaterial in tube 6 was then sent via line 1 into detarring flask 6 whereheavy fractions formed during the pyrolysis of the crude stock in tube 6were separated. The gases or vapors in. flask 9 were then led throughline into flask [2 which was cooled by immersion in ice bath l3. Flaskl2 functions as a condenser and liquefles the major portion of theproducts contained in the vapors passing to this flask. The materialswhich are not condensed in flask 12 pass via tube 16 to sulphuric acidscrubber where any basic substances present are collected.

As a result of this experiment a portion of the crude stock contained inflask 2 was converted into pyridine bodies in pyrolytic zone 6 andcollected in flask 12. The yield of pyridines obtained by thisexperiment was found to be 10% of the theoretical yield based upon thequantity of charging stock sent or transferred from flask 2 through thepyrolytic zone 6.

The same experiment was repeated using A1203.Si02 as catalyst inpyrolysis tube 6. This catalyst was prepared by neutralizing Na2SiO3 toa pH value of 6 or 7 with a water solution of A12(SO'4)3. As a result ofthis neutralization A12O3.SiO2 separated in a white, grainy condition.The granular Al2O3.SiO2 was thoroughly washed with water and thenthoroughly dried for a period of 2 hours. The dried material was thenheated at 700 C. for a period of hours with the result that a grainy,porous material was obtained.

Using the above catalyst, C16H25N as the charging stock, natural gas asthe carrier and a temperature of 700 C. in the pyrolysis tube 6 a yieldof pyridines equal to 70% of theoretical, based on the raw stocktreated, was obtained. In other words, pyrolysis of 50 grams of theC1BH25N base with the aluminum catalyst yielded 11 grams of pyridinesand 20 grams of the original base. This crude mixture was purified asfollows: The crude material was thoroughly sulphited with S02 at 20-25C. The sulphited mass was then heated at 100 C. for a period of twohours to drive oil a portion of the contained S02. As a result ofdriving off a portion of the S02 (which is known as degassing) some ofthe original base layered out and was decanted away. Caustic was thenadded to the aqueous layer and the oil liberated by this treatment wasrecovered and picrated to a crystalline salt. This salt wasrecrystallized from water twice and once from dilute ethyl alcohol. Thepurified. crystals obtained were long slender yellow nee dles having amelting point of 146-148 C. From the analytical data obtained from thispicrate the formula Cal-InN was derived. 7

In a further experiment using the same temperature, catalyst, base,etc., but using a longer" theoretical.

While we have described the use of an aluminum oxide catalyst as an aidin the pyrolysis of the crude nitrogen base material to pyridine we donot wish to limit ourselves to this catalyst since we have found thatother dehydrogenating catalysts such as molybdenum oxide and chromiumoxide may also be used.

Three crude nitrogen base fractions containing no pyridines havingboiling point ranges within 05 C. of 200, 210 and 220 0., respectively,recovered from kerosene extract by acid extraction were separatelypyrolyzed as follows:

Seventy five grams of each of the above bases were pyrolyzed at 700 C.in the presence of A12O3.Si02 catalyst, using natural gas as the basecarrier, as described in connection with the figure. The time employedto pass the 75 gram samples of the crude bases through the pyrolyzingzone was 1 hours.

The distillates obtained by these three pyrolytic experiments werecollected and examined.

From the distillate obtained by the pyrolysis of the 75 gram sample of200 C. boiling point crude base there was recovered 5.3 grams ofpyridines having a boiling point of 205 C. at 746 mm. and a refractiveindex of (n25/D) 1.5010; 7.1 grams of pyridines having a boiling pointof 216 C. at 746 mm. and a refractive index of (n25/D) 1.5024; and 18.6grams of pyridines having a boiling point of 224 C. at 746 mm. and arefractive index of (n25/D) 1.5030. The total yield of pyridines in thiscase was therefore 31.0 grams and the total percent recovery on theweight basis of charging stock and pyridine recovered was 41%.

From the distillate obtained by the pyrolysis of the 75 gram sample of210 C. boiling point crude base there was recovered 6.7 grams ofpyridines having a boiling point of 214 C. at 746 mm. and a refractiveindex of (n25/D) 1.5040;

20.1 grams of pyridines having a boiling point of 228 C. at 746 mm. anda refractive index of (n25/D) 1.5060; and 6.0 grams of pyridines havinga boiling point of 234 C. at 746 mm. and a refractive index of (n25/D)1.5132. The yield of pyridines in this experiment was 32.8 grams or1.5126, and 3.8 grams of pyridines having a boiling point of 246 C. at736 mm. and a refractive index of (n'25/D) 1.5148. The total yield ofpyridines in this experiment was therefore 84.5 grams or 45.5% of theweight of the crude base pyrolyzed.

A further pyrolysis experiment was performed upon a 100 gram sample ofcrude nitrogen bases having a boiling point of 275 C. and composedapproximately of 85% non-aromatics and 15% aromatics. These bases werederived from kerosene bases of 275-280 C. boiling point range. Thesebases were pyrolyzed at 700 C. in .the presence of the Al2O3.SiO2catalyst, using natural gas as the base carrier, The distillatecollected as a result of the pyrolysis was examined and found to contain20 grams of mixed quinolines and pyridines with an initial boiling pointof 225 C. at 746 mm.-and a refractive index of (n25/D) 1.5025 and 30grams-ofunreacted charging stock.

1- This was a yield of 29% based on the pyrolyzed charging stock.

Furthermore '50 grams of a crude non-aromatic base having a boilingpoint of 275 C. was pyrolyzed as described above in the presence of131203.510: catalyst at 700 C. using natural gas as the carrier for thecrude bases, From the distillate collected from the pyrolysis tube therewas obtained 11 grams of pyridines having a boiling point of 180 C,which picrated nicely indicating a simple mixture.

In another experiment crude kerosene bases boiling between 270 and 280C. were dissolved in aqueous hydrochloric acid and extracted withchloroform. The chloroform extracted the nonaromatic or hydro-aromaticbase hydrochlorides from which free bases were obtained by evaporationof the chloroform and treatment of the salts with caustic alkali. Thesefree bases were then condensed with an excess of phthalic acidanhydride, whereby 78% formed phthalones. The residual 22%, comprisingnon-aromatic or hydroaromatic bases uncondensable with phthalicanhydride, and which had a refractive index (1225/13) of 1.5123 was thenpyrolized at 700 C. over an A1203.S1O2 catalyst. From a charge of 115cc., 53.0 cc. of acid soluble condensate were obtained. This condensatewas then fractionally distilled to give cuts ranging in boiling pointfrom 172 C. to 293 C. The fractions boiling below 200 C. were found tobe pyridines, while the fractions boiling from 200 to 293 C. were foundto be mixtures of quinolines and pyridines together with a smallquantity of unchanged original material. Only the lowest boilingfraction (172 C.) was found to have a refractive index (n25/D) 1.4962lower than the material pyrolyzed (boiling point 270 C., n25/D 1.5123).The remainder of the fractions had refractive indices (n25/D) rangingfrom 1.5232 to 1.5844.

The catalysts used in our process should be capable of effectingdehydrogenation. We find that difiicultly reducible metallic oxides aresuitable for this purpose, particularly the mixed oxides of aluminum andsilicon. Contact masses such as pumice are also effective, We observebut little pyrolytic action at temperatures lower than 400 0., whereasat 700 C. substantial pyrolysis was obtained. Higher temperatures arealso suitable, but excessively high temperatures which induce completepyrolysis or degradation of the organic nitrogen compounds should beavoided.

It is to be understood that the disclosures here made are to beconsidered as illustrative and not as limiting except as required by thestate of the prior art.

We claim:

1. A method of treating nitrogen bases having the general formulaC16II25N and derived from petroleum distillates, which comprisesconducting the vapors of said bases at a temperature of about 700 C.over a contact mass composed of complex salts of oxides of aluminum andsilicon, collecting the products of reaction, and recovering pyridinestherefrom.

2. A method according to claim 1 in which the nitrogen base vapors areborne by a carrier gas.

JAMES R. BAILEY. RAYMOND MAHAN.

